Mobile telephony using a prepaid service has driven the growth of penetration rates in data networks in many markets. A prepaid service is a billing arrangement between an operator of a data network and a customer, hereinafter also called subscriber, where the subscriber deposits and amount of money in advance which is subsequently used to pay for usage of network services like for instance telephone calls, data transfer between a telephone or computer and data resources in the internet. Such usage of data network services will hereinafter be named network session.
To get full control of the customer credit, a prepaid service is usually based on an on-line charging process. Charging is understood as a set of functions whereby information related to a chargeable event (charge information) is formatted and transferred in order to make it possible to determine usage for which the charged party may be billed. A chargeable event maybe the transport of data between given terminal devices, e.g., telephones, handhelds or computers, through the bearer network, or a service rendered like establishing a radio transmission telephone session, or the delivery of content, like for instance stock market data stored in a database, etc. In an on-line charging process charging information can affect, in real-time, the service rendered. An on-line charging process therefore directly interacts with the network session control.
Due to its success in existing markets prepaid functionality is therefore an essential feature also for the growing third generation (3G) networks. To date, however, existing mechanisms do not allow providing full prepaid functionality to roaming subscribers. Currently offered prepaid services are not flexibly available in a visited network.
Some services use real-time charge calculation methods in which a calculation algorithm is implemented in a terminal device, e.g. in a chip integrated into a prepaid card. This method is expensive because it requires the implementation of the algorithm in each terminal device. It also restricts the flexibility of the charging system of the network operator since the algorithm can usually not be changed.
U.S. Pat. No. 6,226,364 describes a data network and method enabling real-time online charging of data network subscribers. The network's charging system may also obtain temporary service profiles for visiting roamers. For this the charging system downloads customer service information for the roamer from a roamer clearinghouse. The roamer's customer service information is then entered into the network's charging system as a temporary customer service profile and account for the roamer. As service is provided to the roamer, the billing system recalculates the prepaid balance or outstanding postpaid balance, and updates these parameters in the roamer's temporary customer service profile. Once the roamer stops receiving service from the host telephone service provider, the updated customer service information is posted back to the roamer clearinghouse.
This method has the disadvantage of requiring administrative effort for running the roamer's clearinghouse and for keeping temporary customer's files in the visited network. It is therefore complicated and expensive.